Hand instruments of the prior art commonly in use in dental care comprise a substantially elongated handle part, at least one end of which is typically arranged with a head part protruding substantially in the direction of the central axis of the handle. The head part used in such instruments is usually attached to the handle part as fixed, i.e. the instrument is designed such that changing the head part to a new one is not possible in practise.
The instrument designed to be used manually may be e.g. one designed for removing tartar, which includes a substantially narrow head part with at least one bending. The sharp head parts of this type of instruments tend to become blunt over time during use. Working efficiency and comfort of use are not at the same level when using a blunt instrument instead of a sharp one.
Devices designed to sharpen head parts are known in the industry. If these devices are used at the dentist's office, the time spent for sharpening is always away from something else. On the other hand, by sharpening one does not necessarily reach an end result that would correspond to the original, but one may end up with a damaged or even a completely ruined instrument. Traditionally, there has been just one option for sharpening the head part: to get a new instrument.
On the other hand, there always are dentists who would e.g. in connection with tooth filling want to use instruments which are equipped with another kinds of head part combinations than those the instrument manufacturers in the dental field normally have to offer. It is quite difficult or often almost impossible in practise for the instrument manufacturers to meet these wishes because the price of special instruments manufactured individually or in small quantities tends to become excessively high.
Instruments for the dentist have been available which allow for changing of the head parts. These prior art constructions have certain problems, though, which have not been likely to increase popularity of the instruments with interchangeable head parts. One known solution has been to arrange both the head part as well as the handle part with compatible threads. However, this kind of solution easily results in that the new head part doesn't get positioned to the same radial orientation with respect to the central axis of the handle part as the head part previously used. This may be awkward in instruments which have head parts at both of their ends because the mutual position of the head parts is not such anymore as the user had got used to. In this case, when changing over to using the other head part, one first has to twiddle the instrument in one's hand with respect to the orientation of the head part, in order to find the correct operation angle. Further, changing a head part to a new one is also a fairly laborious and time-consuming operation in case one has to use tools for detaching and attaching the head part, in some prior art implementations even special tools particularly designed for the use in question. In such case, it may also turn out to be a problem that the tool or tools needed to change the head part have not been kept safe or that they are at least not available when the need to change the head part arises.